Mayor de Blasio has found another target in his ongoing war against the parts of this city that work.

First came the NYPD and charter schools. Now it’s the park conservancies — organizations funded with private donations to maintain public parks.

He wants them to cough up some of their money and redistribute it to lesser-known or less-well-off parks.

It’s supposedly “voluntary,” but the “or else” is understood by everyone.

The mayor’s de facto shakedown came during a recent news conference, where he announced that the city will spend $130 million for the upkeep of smaller parks.

“The public sector is putting our money where our mouth is,” de Blasio said. “We will…also turn to the major parks conservancies…[and] expect to get some real important contributions from the conservancies, as part of these processes.”

In fairness, it’s not a new argument for him; he campaigned on it.

The problem is, it misses the whole point of why we have these conservancies in the first place: Because the government can’t do basic tasks, such as maintaining parks.

Take the Central Park Conservancy, the mayor’s No. 1 target. It was created 34 years ago, precisely because the city was broke and the park was in disrepair.

As a result, private donors now pay for 75 percent of the upkeep each year — some $46 million — for Manhattan’s crowning jewel.

Diverting those dollars would violate the promises made to donors when they gave their money.

Besides, it’s not like the conservancy isn’t already contributing more than its fair share. Its $46 million would otherwise come from the city budget.

A 2009 study found that the park generates nearly $400 million in economic activity for the city — plus another $650 million from related real estate and other revenues.